A balun device is a transformer connected between a balanced terminal and an unbalanced terminal. The balanced terminal is connected to a balanced impedance and the unbalanced terminal to an unbalanced impedance. For example, the balanced terminal can be connected to either a source or load impedance of a matching circuit or an amplifier device. Similarly the unbalanced terminal can be connected to either a load or source impedance of the matching circuit or amplifier device.
Electronic devices generally include input or output balanced terminals such that differential signals can be used to for example improve common mode rejection, cancel out signal offset, noise, and the like. It is desirable to combine differential signals in order to generate a single-ended signal to be processed. A balun device is suitable to convert differential output signals into an output signal of the single-ended type.
Baluns can be manufactured on printed circuit boards (PCBs). Typical baluns include a first portion that is manufactured by means of a metal track printed on one of the planar surfaces of the PCB and a second portion that is manufactured with a coaxial cable which is connected to the first portion on the same planar surface. The terminal ends of the first portion are usually connected to corresponding terminal ends of the coaxial cable by for example welding. However, these known baluns cannot be manufactured with sufficient reproducibility, need to be manually welded, and have a large footprint.